? re: Poor draining soil under deck.

I live in NC with clay soil. A problem area for me is under my deck where the soil NEVER seems to drain. I've removed the mulch installed by the builder. :-( to try and help to no avail. I don't want the deck supports to prematurely rot out from underneath us!
Is it possible/adviseable to install a membrane/barrier on top of the soil to only permit evaporation and no further water uptake?
Could/should I also add crushed rock to assist in draining the water away from this area?
Rob
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the snipped-for-privacy@nospam.yahoo.com wrote:

I hope the deck supports are not resting on the ground. Does the ground slope away from the house?
--

Travis in Shoreline (just North of Seattle) Washington
USDA Zone 8b
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Travis wrote:

The deck supports are embedded in concrete. The ground does slope away from the house. The soil is just like a big sponge.
Rob
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If you have positive drainage topographically away from that space, then the problem lies in both the moisture retentive qualities of the below deck soil, as well as the inability of the surrounding soil to translocate the water away below ground. Many different possibilities exist for why exactly that's happening, but the solution you propose is not a good idea.
Are you familiar with how to identify what types of soil you have? (sandy, silty, loamy, etc?)
-- David J. Bockman, Fairfax, VA (USDA Hardiness Zone 7) email: snipped-for-privacy@beyondgardening.com http://beyondgardening.com/Albums
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David J Bockman wrote:

David- This is the problem as you state. Do you have any solutions to share?
The soil is so wet all the top an identfication of type is difficult for me.
Rob
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I really can't suggest solutions without knowing more about the soil conditions. either the soil itself is suspect (marine clay, or something similar) or there is some sort of physical barrier keeping that area from draining. Other possibilites are leaky sewer lines or water lines...
If it were me, I'd get under the deck and shovel out a hole going about 2 feet down. I'd dump the soil onto a tarp and then drag it out into the sun until it dries, then I would examine it. You can plot your results on a three sided chart which I've posted to alt.binaries.pictures.gardens as 'soil makeup grid' which is widely used to classify soil types. The diagram shows a three sided grid with each side representing the content of a particular particle on a scale from 0% to 100%. The bottom line is the sand content, starting at 0% at the bottom right hand corner, and rising to 100% in the bottom left hand corner.
-- David J. Bockman, Fairfax, VA (USDA Hardiness Zone 7) email: snipped-for-privacy@beyondgardening.com http://beyondgardening.com/Albums
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David J Bockman wrote:

It sounds easy, but it isn't quite as easy as it sounds. The differentiation of the soil components isn't just a matter of judgement. Our local extension service charges around $50 for a soil classification. However, I spotted a link that tells you in detail how to do it yourself. I haven't tried it (New England soil is still fairly solid at this time of year) so I don't know how easy or reliable it is. But it's cheap, and therefore worth a shot.
http://everything2.com/?node_id 98166
In case you're not familiar with the soil triangle, an example can be found at http://www.oneplan.org/Water/soil-triangle.shtml (There are lots of them out there. Google it. The above link was the first one.)
On the subject of soil tests for the garden, I recommend that if you are using a home soil test kit you spring for a professional test at least once to compare their results against your kit. The home kit pH tests are reasonable, and the potassium and phosphorous are probably not too bad, but the nitrogen home test is not really very reliable.
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dps Wrote:

Hi Rob, You've gotten some great advice here, so I won't repeat that, but thes sites show how to dig your trenches and do the piping. I would thin that you might also be concerned about the water against th foundation. The gnats are probably fungal gnats due to all tha moisture. It could also become a mosquito problem with the war weather. http://tinyurl.com/6gyux http://tinyurl.com/3wpno http://tinyurl.com/5p4fq http://tinyurl.com/4svjp http://tinyurl.com/6labr http://tinyurl.com/5hrpy
I'm not a use.net poster, but posting from a forum, so forgive me fo not knowing how to snip and paste all the conversations.
New
-- Newt
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the snipped-for-privacy@nospam.yahoo.com wrote:

The deck supports should be sitting on top of concrete footings or, possibly, embedded in concrete. If they are just buried in the soil, you may have problems with settling, as well as water.
It's a little odd that the builder would put mulch under the deck. Is this a raised deck that you can walk underneath?
First, make sure your gutters aren't draining anywhere near the deck.
If there is a lower region of your yard in easy reach, I would dig a trench and line the bottom with plastic sheeting. Put in a length of corrugated, perforated pipe, and fill the trench with crushed rock. The water will now drain from under your deck to the lower area.
If trenching isn't feasible, you may be able to dig a pit, install a sump pump, and pump the water away.

Any covering, whether a membrane or crushed rock, will reduce evaporation unless you deal with the underlying drainage problem first.
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snipped-for-privacy@yahoo.com wrote:

Yes, it is tall enough to walk under but, when it warms up the gnats tend to keep one away.

Luckily, they aren't.

I like the trench idea. Would this solution also help drain the exsisting water-logged soil or just help shedding when it rains? Should I slope the earth towards the trench in the middle or, dig several trenches?
Rob
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the snipped-for-privacy@nospam.yahoo.com wrote:

As long as you don't line the sides of the trench with plastic all the way to the top, it should drain the existing water logged soil as well as catching surface runoff. It may not even be necessary to line the bottom with plastic sheeting, but I think it would help direct any water that doesn't enter the pipe. The water will seek the lowest point, so it will seep through the walls of the trench and flow away through the pipe. Eventually, the water table should be level with the bottom of the trench, instead of at the surface.
If you can find the lowest point under the deck, I'd start the trench there. It may not be necessary to dig multiple trenches. Make sure the trench always runs downhill until you get to the place where you want the water to drain out. Don't forget to put a nylon "sock" around the perforated pipe (available along with the pipe at Home Despot or Lowes) so that silt doesn't clog the pipe in a couple of years.
Once the trench is away from the waterlogged area, you could convert from perforated to solid pipe and bury it under soil and plantings instead of having a gravel filled trench.
I live in NC, too, and I've been digging similar trenches to drain water away from the back of our house. I've also connected the gutters to solid-walled pipe that runs through the same trench.
My only other piece of advice is to try to dig when the soil is damp but not soaked (though that may not be possible in the waterlogged area). When our clay is wet, it is incredibly sticky and permanently stains clothes. When it is dry, it's like cement.
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